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                            <div style="color:gray; word-break: break-all; font-size:12px;">原英文版地址: <a href="https://www.elastic.co/guide/en/elasticsearch/reference/7.7/input-chain.html" rel="nofollow" target="_blank">https://www.elastic.co/guide/en/elasticsearch/reference/7.7/input-chain.html</a>, 原文档版权归 www.elastic.co 所有<br/>本地英文版地址: <a href="../en/input-chain.html" rel="nofollow" target="_blank">../en/input-chain.html</a></div>
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<strong>重要</strong>: 此版本不会发布额外的bug修复或文档更新。最新信息请参考 <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html" rel="nofollow">当前版本文档</a>。
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<h2 class="title">
<a id="input-chain"></a>Chain input<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/x-pack/docs/en/watcher/input/chain.asciidoc">edit</a><a class="xpack_tag" href="https://www.elastic.co/subscriptions"></a>
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<p>Use the <code class="literal">chain</code> input to load data from multiple sources into the watch
execution context when the watch is triggered. The inputs in a chain
are processed in order and the data loaded by an input can be accessed by the
subsequent inputs in the chain.</p>
<p>The <code class="literal">chain</code> input enables you to perform actions based on data from multiple
sources. You can also use the data collected by one input to load data
from another source.</p>
<p>For example, the following chain input loads data from an HTTP server using the
path set by a <code class="literal">simple</code> input:</p>
<div class="pre_wrapper lang-js">
<pre class="programlisting prettyprint lang-js">"input" : {
  "chain" : {
    "inputs" : [ <a id="CO510-1"></a><i class="conum" data-value="1"></i>
      {
        "first" : {
          "simple" : { "path" : "/_search" }
        }
      },
      {
        "second" : {
          "http" : {
            "request" : {
              "host" : "localhost",
              "port" : 9200,
              "path" : "{{ctx.payload.first.path}}" <a id="CO510-2"></a><i class="conum" data-value="2"></i>
            }
          }
        }
      }
    ]
  }
}</pre>
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<p><a href="#CO510-1"><i class="conum" data-value="1"></i></a></p>
</td>
<td align="left" valign="top">
<p>The inputs in a chain are specified as an array to guarantee the order in
which the inputs are processed. (JSON does not guarantee the order of
arbitrary objects.)</p>
</td>
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<p><a href="#CO510-2"><i class="conum" data-value="2"></i></a></p>
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<p>Loads the <code class="literal">path</code> set by the <code class="literal">first</code> input.</p>
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<h3 class="title">
<a id="_accessing_chained_input_data"></a>Accessing chained input data<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/x-pack/docs/en/watcher/input/chain.asciidoc">edit</a>
</h3>
</div></div></div>
<p>To reference data loaded by a particular input, you use the input’s name,
<code class="literal">ctx.payload.&lt;input-name&gt;.&lt;value&gt;</code>.</p>
</div>

<div class="section">
<div class="titlepage"><div><div>
<h3 class="title">
<a id="_transforming_chained_input_data"></a>Transforming chained input data<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/x-pack/docs/en/watcher/input/chain.asciidoc">edit</a>
</h3>
</div></div></div>
<p>In certain use-cases the output of the first input should be used as input
in a subsequent input. This requires you to do a transform, before you pass
the data on to the next input.</p>
<p>In order to achieve this you can use a transform input between the two
specified inputs, see the following example. Note, that the first input will
still be available in its original form in <code class="literal">ctx.payload.first</code>.</p>
<div class="pre_wrapper lang-js">
<pre class="programlisting prettyprint lang-js">"input" : {
  "chain" : {
    "inputs" : [ <a id="CO511-1"></a><i class="conum" data-value="1"></i>
      {
        "first" : {
          "simple" : { "path" : "/_search" }
        }
      },
      {
        "second" : {
          "transform" : {
            "script" : "return [ 'path' : ctx.payload.first.path + '/' ]"
          }
        }
      },
      {
        "third" : {
          "http" : {
            "request" : {
              "host" : "localhost",
              "port" : 9200,
              "path" : "{{ctx.payload.second.path}}" <a id="CO511-2"></a><i class="conum" data-value="2"></i>
            }
          }
        }
      }
    ]
  }
}</pre>
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